HAMILTON, Ontario, Dec. 23 (UPI) — Prolonged exposure to higher levels of air pollution can lead to hospitalization for pneumonia in adults age 65 and older, Canadian researchers found.

Infectious disease specialist Mark Loeb of McMaster University’s Michael G. DeGroote School of Medicine in Hamilton led a research team in recruiting 365 older adults from Hamilton who had been hospitalized with radiologically confirmed pneumonia from July 2003 to April 2005. Control subjects randomly selected from the same neighborhoods as the patients were also enrolled in the study.

The researchers used structured interviews to collect health data from participants and compared the two groups’ exposures to data from air-quality monitoring stations and land-use regression models.

The researchers found that exposure for more than 12 months to higher levels of nitrogen dioxide and fine particulate matter of less than 2.5 micrometers more than doubled the risk of hospitalization for pneumonia in adults age 65 and older. However, exposure to sulfur dioxide was not associated with an increased risk of hospitalization.

“Our study found that among older individuals, long-term exposure to traffic pollution independently increased their risk of hospitalization for pneumonia,” Loeb said in a statement.

The findings are scheduled to be published in the Jan. 1 issue of the American Journal of Respiratory and Critical Care Medicine.